THE VARIATION OF THE VISCOSITY OF GASES WITH TEMPERATURE OVER A LARGE TEMPERATURE RANGE

Abstract

The coefficients of viscosity of ammonia, propylene, ethylene and methyl ether, over the temperature range 23 to −80 °C., have been measured. A comparison is made between the present data and those of other authors for temperatures above 0 °C. It is estimated that the authors' results are correct to 0.2% and have a relative accuracy of 0.1%. It is claimed that they are the most accurate data for the viscosity of gases at low temperatures to date.The validity of a number of viscosity–temperature relations has been tested with the present data and those previously published (18, 20). In general, it is found that the equations of Sutherland and Jones hold at high temperatures but fail at low temperatures for substances such as carbon dioxide, sulphur dioxide, ammonia, methyl ether and propylene, which have viscosity–temperature curves that are convex to the temperature axis below room temperature. An empirical equation is suggested which adequately represents the variation of viscosity with temperature for these five gases over the temperature range 23 to −80 °C. However, this relation fails at high temperatures for all gases, and even at low temperatures for substances such as hydrogen, air and ethylene.It is pointed out that the viscosity–temperature curves for carbon dioxide, sulphur dioxide, ammonia, methyl ether and propylene each show a definite inversion or inflexion point. Below this inversion temperature the viscosity curves are convex to the temperature axis; above it they are concave to the temperature axis. In general, it seems that this inversion temperature bears a direct relation to the polarity of the molecule and to the critical temperature.